The purpose of this study is to identify the neural connections of the accessory optic nuclei, i. e. medial, lateral, and dorsal accessory optic nuclei. The efferent projections of the nuclei will be determined autoradiographically following stereotaxic placement of injection probes and iontophoresis of tritiated radioisotopes. This will permit the tracing of labelled proteins which are transport by axoplasmic flow from the injection site to their point of termination. Some attempt will also be made to label and trace pathways by the horseradish peroxidase method (HRP). It is hoped that this study will clarify the relationship of the accessory optic system to the visual system and also lead to functional inferences that can be listed behaviorally.